1. Field of the Invention
The invention relates to fusible chlorine-free vinyl acetate copolymer fibres, to processes for their production and to their use as fibrous binders.
2. Background Art
To increase the resistance to mechanical load, fibrous structures, for example nonwoven fabrics, are bonded with binders. These binders can be employed in the form of solids, such as powders or fibres, or as liquids, in the form of solutions or dispersions. Fibrous binders have a number of advantages over aqueous binder dispersions. Bonding nonwovens by means of aqueous dispersions requires a special application machine and a drying unit for removing the aqueous phase from the dispersion. In addition to the expenditure on apparatus, the removal of water is also very expensive in terms of energy. In contrast, fibrous binders can be processed on the customary devices for production of textile sheet-like structures together with the fibres to be bonded. For example, the binder fibres can be laid out together with the fibres to be bonded, and the fibre material can be bonded with a far lower energy consumption by heating to the melting point of the binder fibres.
Conventional melt-fusible fibres which are employed for bonding textile sheet-like structures are, for example, polyolefins, such as polyethylene or polypropylene fibres, or polyesters, such as polyethylene terephthalate fibres. Nevertheless, these fibres have the disadvantage that their melt viscosity changes dramatically within a narrow temperature range. During processing of these fibres, the temperature and residence time during thermal bonding must be adhered to very precisely, since even small variations in temperature can cause the molten fibrous binder to run-off.
A wider temperature range for processing is available with copolymer fibres (CP fibres) based on vinyl acetate/vinyl chloride copolymer fibres. A disadvantage of these fibres is the high chlorine content, which leads to problems during disposal and re-use of textiles bonded therewith.
The object was therefore to provide a fusible thermoplastic fibre which has the same melting characteristics as the CP fibres but does not contain any chlorine. In addition, it should be possible to melt-spin the polymer, in order to bypass the disposal problems of polymers which can be spun only in solution.